Treat all warnings as errors

[crud89]

Because warnings demand just as much attention as errors. The compiler should successfully compile the code after specifying the /WX flag for release builds.

This only applies to internal warnings. Warnings from external libraries are currently suppressed by specifying the /experimental:external /external:W0 compiler flag. This only works for Visual Studio 15.6 or higher.

Requires Issue #1 to be resolved first.